The present invention relates generally to methods and apparatus for taking dimensional measurements of objects and, more specifically, to a method and apparatus for ascertaining three-dimensional measurements and/or volume of objects and methods of use and calibration of same.
Millions of packages per year are handled and shipped by United Parcel Service, Federal Express, and many other smaller courier and delivery services. These packages originate with federal, state, and local governments as well as private businesses of all sizes. In many instances, the charges by the carriers to their customers are based on the so-called "dim-weight factor" or "dimensional weight factor" (DWF) of the article being shipped, a fictitious dimension based on length times width times height in inches divided by a standard agency or association-recognized divisor or conversion factor, commonly 166 (L.times.W.times.H.div.166). The "166" divisor or conversion factor has been recognized and adopted by the International Air Transport Association (I.A.T.A). Even if an object or package is of irregular configuration, the dim weight, using the longest measurement each of length, width, and height, is still utilized for billing purposes. The volume computed by multiplication of object length times width times height may hereinafter be termed the "cubic volume," "spatial volume," or simply the "cube" of the object.
The measurements of the articles shipped are also critical so that the carrier can accurately determine the number of trucks, trailers, or other vehicles which will be required to transport goods to their destinations and so both customers and carriers can accurately estimate their warehousing and other storage needs.
In addition, article weight and measurements are also used to determine and predict weight and balance for transport vehicles and aircraft and to dictate the loading sequence for objects by weight and dimensions for maximum safety and efficiency.
Further, if orders of any items are to be packed into boxes, knowledge of object weight and dimensions would be useful for selecting box size and durability.
To date, it has been a common practice for the customer to manually "cube" or measure boxes or other articles with a ruler, yardstick, or other straightedge marked with units of length, generally inches, perform a calculation for "dim weight," and provide same to the carrier with the package. If the customer does not "cube" the articles, then the carrier performs the operation. Since these measurements and calculations are generally done hurriedly, there is an equal chance that the customer will be under or over charged. To add to the problem, there are many packages and other objects not susceptible to even a grossly accurate manual measurement of dim weight, for example and not by way of limitation, loaded pallets, tubes, drums, reels of hose, cable or wire, etc. Many machine and automotive parts are shipped "naked" with tags attached or, at most, bagged or shrink wrapped. It is obvious to one skilled in the art that a straightedge measurement to ascertain the greatest extent of each dimension will not be accurate in any of these instances to any degree whatsoever.
It is known to the inventors that a "jig"-type measuring system for packages has been used, with a base and two sides joining in a corner at 90.degree. angles, each marked with gross dimensional units (to the nearest one inch) so that a cubic package can be placed on the base at the corner and measurements taken manually by looking at the markings and recording same, but again, the accuracy is limited by the care and eyesight of the measurer, and the time utilized is unreasonably long when thousands of packages are being shipped, as with Sears, K-Mart, or other large retailers.
In short, a quick, accurate means and method for determining the dimensions and the cubic volume or spatial volume of packages and other objects in a commercial or industrial setting has been lacking for many situations.
U.S. Pat. No. 5,042,015, assigned to the assignee of the present application, discloses practical and commercially successful means and methods for such object measuring of both stationary and moving objects, although the apparatus of the '015 patent requires that moving objects be aligned with the path of movement.
U.S. Pat. No. 5,105,392, assigned to the assignee of the present application, provides alternatives and improvements to the system of the '015 patent. The '392 patent discloses and claims a method and apparatus for three-dimensional measurement of large and irregular objects, such as palletized loads. The '392 patent also discloses and claims a method and apparatus for determining the actual length and width dimensions of randomly-aligned linearly moving rectangular objects by determining apparent length, apparent width, and the distance between an object corner facing to the side of the travel direction and the trailing edge of the object. These measurements were then employed to determine the actual object length and width via trigonometrically-based mathematical equations.
The methodology for moving object measurement as described in the '392 patent has been proven to be sound, as have the mathematical relationships, and has also been applied in U.S. Patent application Ser. No. 07/843,008, filed Feb. 28, 1992, now U.S. Pat. No. 5,220,536 and assigned to the assignee of the present application. The '008 application discloses and claims a method and apparatus for determining the length, width and height of randomly-aligned packages and other substantially rectangular objects by utilization of a combination of a light curtain and an ultrasonic distance sensor.
While the apparatus and methods of the foregoing patents and application have been extremely successful in the market and have, in fact, created an unprecedented commercial and industrial demand for dimensional measurement, these advances have also pointed toward a need for some refinements which may further enhance their utility and accuracy.
For example, the apparatus disclosed and claimed in the '015 patent for weighing and dimensional measuring of objects, illustrated in FIGS. 1 through 4 of this application and described on pages 9 through 26 of this specification, requires that an object to be measured be placed at a "zero point" 36 or 120 on a surface supporting the object for an accurate measurement of object length and width. If the object is not at the zero point when the sensors are activated, the apparatus will indicate a larger and false object length and/or width, depending upon the exact placement of the object and whether or not a moving object is being measured.
Similarly, and with particular reference to the apparatus of FIGS. 3 and 4, although other embodiments of the invention may be similarly affected, if an object is placed too close to an ultrasonic sensor (such as 14, 16 or 18) or too large an object is placed within the volume defined by the placement of sensors 12, 14 and 16 with respect to zero point 120, a false reading will result as the receiver of the ultrasonic sensor cannot react fast enough to convert the extremely short reflected ultrasonic wave travel time between the emitter, the object surface, and the receiver. Therefore, the receiver may not provide a meaningful signal indicative of any volume or, even worse, may pick up a previously-reflected ultrasonic wave which has subsequently reflected off of the sensor face, back to the object surface, and then back to the emitter. In such an instance, the increased wave travel time would be correlated to a smaller-than-actual object dimension and result in inaccurate storage or cargo placement or billing.